I’m aware of this!  I’m pointing out to get to “grid scale” is hundreds/thousands of hectares of land consumed by storage units.
Pumped hydro, well, I was deeply involved in a project (we have a few of those 4,500 suitable sites).  Had plenty of meetings of all types with the AER, power networks, the wholesalers.  Worked on the modelling for behind/in front of meter options.  Worked on route to market upgrades including stakeholder engagement with landowners.  Worked with the design team on the storage dams, on the high density concrete structures required, even had a plan to float solar on top of the holding dam to reduce evaporation and add power to the pumping operation.
Project shelved - simply doesn’t stack up.  The economics are horrendous, water usage is borderline criminal due to losses.  The time for the dam to fill before first use was nearly 10 months!
As for grid stability well isn’t it quite cute currently.
LPMA, Castalloy, LBB, and several others all ramp down during high power demand periods.
It buffers the grid, sure, and the government quietly pays the agreed penalties to each group for the inconvenience.
The compensation hourly is quite extraordinary and has to cover lost productivity, refractory damage, reduced asset life due to increased process variability and cycling.
Another subsidy to the renewable grid that isn’t openly known. 

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